In elevator dispatching, the passenger's perception of how long he or she waits for an elevator to arrive has been determined to be non-linear, in the sense that the longer the passenger waits, the more the passenger perceives that he or she has waited longer than the actual wait time. Stated alternatively, the degree of annoyance of waiting is not a linear function of the wait, but increases, perhaps exponentially, with the elapse of time. In U.S. Pat. No. 5,304,752, preferential passenger service is allotted to an individual whose waiting time is longer than the waiting time of all passengers currently waiting for elevator service. In U.S. Pat. No. 4,244,450, the dispatcher uses an increased function of waiting time, which increases with duration of the wait, to dispatch cars more in accordance with passengers' perception of waiting. In that patent, the assignment is based on providing a minimum sum of the overall perceived waiting time for all waiting passengers. Many systems provide for displays that will indicate the time remaining for calls to appear, so that passengers are comfortable with the fact that response is impending; one example is U.S. Pat. No. 5,789,715.